In recent years, multimedia communications over the Internet and other wired and/or wireless communications networks have gained increased popularity. For example, such multimedia communications can be performed within the context of video conferencing systems, in which multipoint control units (MCUs) are employed to facilitate collaboration among groups of conference participant devices by performing various functions including mixing, synchronizing, encoding, decoding, and transcoding video and/or audio data bitstreams generated by the respective conference participant devices.
In such video conferencing systems, successful transmissions of multimedia data between the MCUs and the conference participant devices over communications networks generally require sufficient bandwidth and low latency for minimal packet loss. The MCUs and the conference participant devices are each operative to send and receive multimedia data. Such transmissions of multimedia data between the MCUs and the conference participant devices are typically based on the real-time transport protocol (RTP), and delivery of such multimedia data to the respective MCUs and conference participant devices is typically monitored using the real-time transport control protocol (RTCP). For example, an MCU or conference participant device that receives multimedia data in the form of RTP packets can provide packet error feedback information to the sender of the multimedia data in one or more RTCP feedback packets.
Multimedia communications can be problematic, however, particularly when transmissions of multimedia data are performed over communications networks such as the Internet. For example, when video conferencing is performed over the Internet, various conference participant devices may be subjected to different levels of network congestion, which can result in reduced bandwidth, increased latency, and ultimately increased packet losses, which can severely degrade the multimedia quality of experience (QoE) for conference participants. Moreover, conventional approaches that employ RTCP feedback packets for providing packet error feedback information to senders of multimedia data for use in possible retransmission of lost packets and/or possible transmission of intra-coded frames have heretofore been incapable of reliably achieving the QoE generally desired and/or required for multimedia data transmissions.